A Hall probe (also known as a Hall sensor) is a semiconductor-based detector which uses the Hall effect to measure the strength of a magnetic field. The probe provides an output voltage proportional to the magnitude of a magnetic field. In a conductive material, moving electrical charges (i.e., an electrical current) are affected by a nearby magnetic field. Bending (Lorentz) forces are experienced by the moving charges, which can be described by:Fq=q·vq×B=q·|vq|×|B|·sin(θ)
The result is what may be seen as an orthogonal charge drift, with a build up of either positive or negative charges on the bottom or on the top of the plate. The result of this interaction is a net accumulation of charges on one of the surfaces, and thus the generation of an electric field and a voltage across the terminals which are positioned on orthogonal points to the moving charges (current) and the magnetic field. This voltage (i.e., the Hall voltage) is proportional to the magnitude of the current and the magnetic field as well as the angle between the vectors representing them and the thickness of the conductive material, t. The Hall voltage can be represented as:
      V    H    =                            I                    ×                                  B                          ·                  sin          ⁡                      (            θ            )                                      q      ·      n      ·      t      
Referring to FIG. 1, a conventional planar Hall probe 10 is illustrated for detecting one dimension (z-component) of a magnetic field, B, 12. The Hall probe 10 includes contacts 14a, 14b for applying an electric current, I, flowing through a conductive material 16, i.e. from contact 14a to contact 14b. Voltage terminals 18a, 18b are orthogonally located on the conductive material 16 to the contacts 14a, 14b. A voltage detector 20 can be connected to the terminals 18a, 18b to measure the Hall voltage, VH.
The magnetic field 12 may include an x-component, BX, a y-component, BY, and a z-component, BZ. In FIG. 1, the z-component is illustrated perpendicular to the plane of the electric current, and the x-component and y-component are located on the same plane as the electric current. Accordingly, the Hall probe 10 is a uniaxial device which can only detect the z-component of the magnetic field 12.
In operation, the current is passed through the conductive material 16 which, when placed in the magnetic field 12, a Hall voltage develops across it. The Hall probe 10 may be held so that the magnetic field lines are passing at right angles through the probe (in FIG. 1, the z-component passes at right angles), the voltage detector 20 provides a reading of the value of the z-component of the magnetic flux density (B).
Conventionally, Hall probes can be used for positioning sensors, including angular orientation, for robotics, computing and manufacturing equipment; low-power contactless switching devices for electronic and communication equipment; contactless mechanical counters/rotational devices, for monitoring speed, rotational motion and position in automotive systems; magnetic field measurements, for geological and medical applications; proximity and orientation-sensors, for the low-cost industrial and automotive systems; and the like. Ideally, for all of these applications, small magnetic probes/elements, i.e. MEMS-based, can result in better performance, higher sensitivities, higher space resolutions, lower power consumption, better integration in the overall chip/system, overall low-manufacturing costs, and the like.
Microelectromechanical systems (MEMS) devices are generally made up of components between 1 to 100 micrometers in size (i.e. 0.001 to 0.1 mm) and MEMS devices generally range in size from 20 micrometers (20 millionth of a meter) to a millimeter. Advantageously, MEMS-based Hall probes could provide superior measurement resolution, low-power, improved integration into devices, and the like. However, it is difficult to realize two-dimensional (2D) and three-dimensional (3D) Hall probes simple MEMS processes.
Conventional attempts at multidimensional MEMS-based Hall probes have utilized magneto-transistors as well as a combined use of the Hall and magneto-resistive effects in conductive materials. These existing protocols/methods have several drawbacks including the need for adjustment and interconnection of the subunits, cross-sensitivity, complicated measuring protocols, as well as the fact that the three magnetic field components are not measured at the same point for 3D units.